This paper presents a mathematical model of coordination and optimization of generator and transmission maintenance in electricity market. In this model， security and economical efficiency of power system and fairness of electricity market are taken into account. A hybrid algorithm that takes full advantages of genetic algorithm（GA） and particle swarm optimization（PSO） is applied to solving this model. Population of the hybrid algorithm is divided into two parts that each evolves separately by using GA and PSO respectively. The optimization information of GA and PSO will be exchanged fully to form a new and tight coupled genetic particle swarm optimization（GPSO）. The results of test cases verify that the algorithm proposed has favorable equilibrium on both global and local searches in solving such large-scale complicated optimization problem as the global generator and transmission maintenance scheduling.